Vaccination for protection against sexually transmitted diseases such as acquired immunodeficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV) infection should concentrate on inducing strong antigen-specific humoral and cellular immune responses as a mucosal barrier for viral entry. However, delivery of vaccines, specifically those based on proteins, to the mucosal surfaces is generally inefficient and requires the use of suitable adjuvants that could directly potentiate the effector T cells and the antigen-presenting cells (APC), such as the dendritic cells (DC), and/or mobilize the innate immune responses. The synthetic glycolipid alpha-glactosylceramide (aGalCer), a potent activator of natural killer T (NKT) cells, a major innate immune mediator cell type, has been shown to be safe and effective when administered by the parenteral routes for enhancing specific immune responses to tumor vaccines in several animal model studies. We obtained pilot data showing induction of systemic and mucosal cellular immune responses to HIV as well as non-HIV peptide antigens after intranasal and oral delivery in mice only when aGalCer was co-administered. Based on these results we hypothesize that mucosal delivery of HIV antigens using aGalCer as adjuvant will be a safe and effective approach for inducing strong mucosal and systemic immunity. Furthermore, we hypothesize that DC at mucosal compartments can be activated by aGalCer-mediated NKT cell responses to enable the DC to present HIV antigenic peptides to CD4+ and CD8+ T cells. We propose to harness the adjuvant potential of aGalCer employing the HIV-1 envelope protein, as a test antigen, specifically delivered by the mucosal routes to prime efficient mucosal and systemic immune responses. Our proposed studies will also analyze the underlying mechanisms for the adjuvant activity of aGalCer. To achieve these goals we propose to: Evaluate mucosal adjuvant activity of aGalCer for priming humoral and cellular immune responses to HIV-1 delivered, as protein or expressed from adenoviral vector, by the intranasal and oral routes. Determine potential associations between the kinetics of NKT cell and DC activation and priming of antigen-specific T cells in the mucosal and systemic compartments when aGalCer is used for delivery of antigens by the intranasal and oral routes to mice. Successful outcome (i.e. potent induction of mucosal and systemic antigen-specific immune responses using aGalCer as mucosal adjuvant) will enable us to extend the immunogenicity studies in future proposals for testing HIV/SIV vaccine candidates in the nonhuman primate model comprised of Indian-origin rhesus macaques followed by efficacy testing against mucosal challenge with pathogenic SIV/SHIV strains. PUBLIC HEALTH RELEVANCE: Successful outcome (i.e. potent induction of mucosal and systemic antigen-specific immune responses) will enable us to extend the immunogenicity studies in future proposals for testing HIV/SIV vaccine candidates in the nonhuman primate model comprised of Indian-origin rhesus macaques followed by efficacy testing against mucosal challenge with pathogenic SIV/SHIV strains.